Why does Mariam blame Laiila for marrying Rasheed, and why does she see Laila as a competitor in A Thousand Splendid Suns?Answers with evidence and...

It is simple feminine jealousy that creates the chasm
between Mariam and Laila in A Thousand Splendid Suns. Following the
death of her parents, Laila is nursed back to health in Rasheed's home. Rasheed's motive
soon becomes obvious: He is smitten with the fourteen year old girl, and he wants to
make her his second wife. Laila could have turned him down; after all, there was at
least a 35 year difference in their ages. But Laila has no money and nowhere else to go.
When she discovers that Tariq is dead, there is nothing left to do but accept Rasheed's
proposal. To Laila, Rasheed seems sincere, as he previously appeared to Mariam. Mariam
sees that Rasheed is enamored with the young girl, and she recognizes that her new
position will be that of the second wife: She is the sturdy Volga (a Russian auto),
while Laila will become the Mercedes Benz. Rasheed will now spend his nights with Laila,
and Mariam will become an outcast in her own home. Her jealousy borders on hatred, and
she tells Laila that she will neither be her servant nor her
friend. 

"I
wouldn't have fed you and washed you and nursed you if I'd known you were going to turn
around and steal my husband."